
root@engdebian:~# netstat -nalp | more



Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address       Foreign Address   State       PID/Program name   
tcp        0      0 0.0.0.0:515         0.0.0.0:*         LISTEN       1742/lpd Waiting    
tcp        0      0 127.0.0.1:25        0.0.0.0:*         LISTEN       1726/exim4          
tcp        0      0 192.168.1.101:1040  128.6.238.10:22   ESTABLISHED  2229/ssh            
tcp        0      0 192.168.1.101:1024  128.6.238.12:993  ESTABLISHED  2195/pine           
tcp6       0      0 :::22               :::*              LISTEN       1813/sshd           
udp        0      0 0.0.0.0:68          0.0.0.0:*                      2085/dhclient

Similarly,

netstat -n --inet --listening --programs

Also, the processes responsible for the open ports can be identified with

lsof -i

See example.
Syntax of lsof:

lsof -i [TCP|UDP][@host][:port]

To list all open files for specific processes:

lsof -p PID 
lsof -c COMMAND
lsof -u username

To list all open files

lsof

Exercise
SSH to smbhost VM, become root, and run lsof to see the open internet ports:

ssh 192.168.122.42
sudo -s
lsof -i -P

Note, option "-P" shows you the port number.
You should see the ports opened for the following services: dhclient3, udp/68, sshd, tcp/22.
If you have installed Samba in the previous class, you should also see the Samba related services with their ports, such as smbd, tcp/137,138,139, tcp/445, and nmbd, udp/136,138.